This small extension was slated in a Spanish Grade A slate. The pitch of this roof was only 25 degrees therefore the options on slate size used is reduced and 500mmx 300mm size was the one for this job. On installation the head lap of the slates had to be 125mm to ensure enough cover on each. Using the incorrect slate size and head lap would cause the roof to leak but now worries there when Rooftec are in charge.